1. Field of the Invention
The present invention generally relates to liquid crystal display (LCD) systems, and more particularly to a multi-domains LCD cell structure and a process of forming a LCD substrate.
2. Description of the Related Art
In LCD systems, the liquid crystal molecules are oriented in different directions to selectively allow light passage and thereby achieve image displaying. In the early times of the LCD technique, each pixel cell was operated to orient the liquid is crystal molecules parallel to one single and specific direction to display an image. As a result, the viewing angle of the LCD systems was narrow.
In more recently developed display systems, some techniques have been implemented to mitigate this disadvantage. In this regard, the Japanese company Fujitsu, Ltd has developed a technique in which each pixel cell is divided into a number of domains where the liquid crystal molecules can be aligned along different directions. In this technique, protrusions are provided on the surface of an inner layer in contact with the liquid crystal. The protrusions create boundary conditions that tilt the inclination angle of the liquid crystal molecules differently in each domain, which can provide a wide viewing angle.
FIG. 1 illustrates another technique known in the art for forming a multi-domains LCD without inner protrusions. In FIG. 1, the cell structure 10 includes a liquid crystal layer 15 sandwiched between two substrates 12, 14. A pixel electrode 17 is formed on a surface of the lower substrate 12. A light-shielding layer 19 is formed on a surface of the upper substrate 14 to prevent light leakage. A color filter 22 is formed to cover a portion of the light-shielding layer 19. A common voltage electrode 26 is formed over the color filter 22 and includes recessed portions 28.
When a voltage bias is applied between the pixel electrode 17 and the common voltage electrode 26, the recessed portions 28 of the common voltage electrode 26 act to distort the electric field generated in the liquid crystal layer 15. As a result, the liquid crystal molecules tilt in different directions to produce a multi-domain alignment in the pixel cell.
A disadvantage of the design described in FIG. 1 is that the recessed portions of the common voltage electrode create boundary conditions that undesirably orient the liquid crystal molecules. Therefore, there is a need for a multi-domain LCD that can overcome the disadvantages of the prior art.